1. Field of the Invention
The invention relates to touch sensing, in particular, to a touch sensing apparatus using the charge pump concept to realize the function of analog adder, so that the interference to touch sensing caused by the liquid crystal panel and external environment noise will be reduced to enhance system signal-to-noise ratio (SNR) without an amplifier to lower the cost.
2. Description of the Prior Art
With the rapid progress of technology, the conventional display has been replaced by TFT-LCD gradually, and the TFT-LCD is widely used in various electronic products such as television, flat display, mobile, tablet PC, and projector. As to the TFT-LCD with touch control function, touch sensor is one of the important modules of the TFT-LCD, and the performance of the touch sensor will also directly affect the entire effectiveness of the TFT-LCD.
In general, the conventional LCD with mutual inductance capacitor touch function includes a display panel, an ITO sensor, and a touch control chip. Wherein, the ITO sensor includes a plurality of sensing lines and driving lines, and the touch control chip includes a plurality of pins. The sensing lines are coupled to the pins respectively. After the driving line transmits a driving pulse and couples a small voltage at the sensing line, the touch control chip will sense the coupled voltage and judge whether the ITO sensor is touched according to the coupled voltage.
However, the above-mentioned conventional LCD touch sensing method has serious drawbacks, such as the scanning rate is too low, the operation of the touch control chip is seriously affected by the noise generated by the display panel, even the touch point is misjudged. In order to avoid the noise generated by the panel, a layer of insulating material is disposed between the ITO sensor and the panel; however, this method will increase the cost, and the thickness of the entire apparatus will be increased, it is unfavorable to the design of mechanism. In addition, since an amplifier is necessary for the conventional touch sensing apparatus to amplify the sensed coupling voltage, the die size is hard to be shrunk to lower the cost.
Therefore, the invention provides a touch sensing apparatus using the charge pump concept to realize the function of analog adder to solve the above-mentioned problems.